The pony track (tourist) route was constructed to service the meteorological observatory that opened in 1883, and remains wholly intact. It traverses the SW side of Meall an t-Suidhe, then zigzags the broad west slopes of Ben Nevis to the exposed summit plateau, and consists of a rocky path over steep boulder fields. The problems encountered on this route include the cornices at the head of Gardyloo Gully and Tower Gully, mistaken descent into Five Finger Gully and crossing the top of Red Burn. Despite all this, the Pony Track remains the safest route to take.

Ascending Ben Nevis via the Carn Mor Dearg arete (CMD) route is one of the ultimate classics. Although Carn Mor Dearg is a massive hill itself (9th highest) standing next to "The Ben" this is never really taken into account. The good thing about this route is you see something the tourist path walkers don't see... The north face of "The Ben" what a site!
Staying on the rocky part of the ridge is fantastic with great exposure and scrambling.

Distillery > Carn Beag Dearg > Ben Nevis > Visitors center

10.2 mi

5,000 ft ascent

9-11 hrs

Visitors Center > Carn Beag Dearg > Ben Nevis > Visitors center

11.5 mi

5,800

10-12 hrs

Note: Total ascent is more, because you loose and have to regain elevation in several places.

In winter conditions, unless you are an experienced winter climber with winter equipment, you should not attempt this route as escape is very difficult.
Even in summer, if visibility is bad on the summit it is easy to get into trouble as the path, once lost, is not easily found.

During periods of good visibility the navigation is relatively straightforward but as soon as the mist comes down the plateau can be an extremely confusing and frightening place, especially under conditions of snow and ice. Sound map and compass skills along with a little forethought will go a long way towards avoiding the epics which the unprepared often experience, sometimes with disastrous consequences.
The map below shows how to follow a compass heading of 231° for 150 m then take a heading of 282° to avoid the cliffs at the top.

Walkers on the summit of Britain's highest mountain can now follow a line of cairns to lead them safely to and from its peak.
The Nevis Partnership, which manages Ben Nevis, has rebuilt a line of stone cairns so they mark the recommended compass bearing to be followed to safely navigate off the summit plateau, which has 600m (1,970ft) drops on its north face. In winter, cornices build up on the plateau edges, adding to the hazard for walkers in bad visibility.

Ben Nevis article in Fall 2010 Patagonia catalogue
Conditions: Snow-plastered rock, freezing rain, sleet, whiteout visibility
One trip to Ben Nevis explains, with that knowing head-nod, how so many hardcore alpinists come from a small, low-elevation island near the North Sea. A historical mixed-climbing landmark for good reason, the Ben provides not only challenging climbing but also the full "character building" experience that hardens those with short memories. Sideways-blasting snow and sleet, rain and near-zero visibility make for a good day out and good rime build-up. Of course, you just scrape away the rime and scratch up the rock beneath it, battling upward for security and protection alike, simply dealing with the elements that threaten to strip you off the cliffs.
Refers to rock climbing on the north face, but the walk up the trail can be almost as bad.